1. Field of the Invention
This invention relates to an optical system for converging light beams to form a single beam spot on an optical disc, and more particularly to an improvement of the optical system of an optical disc apparatus.
2. Description of the Related Art
When information is read from or written in an information recording medium in a conventional optical disc apparatus, an objective lens is maintained in a focusing state and a laser beam from a light source is converged by an objective lens so as to form a focused beam spot on an optical disc.
In the conventional optical disc apparatus, a laser beam cannot be converged by the objective lens so as to fall within the diffraction limitation determined by the wavelength of the laser beam. It is considered that the degree of density of the recording and reproduction of information is limited.